Editing Albert Einstein (section)

==== Gravitational waves ====
In 1916, Einstein predicted [[gravitational wave]]s,<ref>Einstein (1916).</ref><ref>Einstein (1918).</ref> ripples in the [[curvature]] of spacetime which propagate as [[wave]]s, traveling outward from the source, transporting energy as gravitational radiation. The existence of gravitational waves is possible under general relativity due to its [[Lorentz invariance]] which brings the concept of a finite speed of propagation of the physical interactions of gravity with it. By contrast, gravitational waves cannot exist in the [[Newton's law of universal gravitation|Newtonian theory of gravitation]], which postulates that the physical interactions of gravity propagate at infinite speed.

The first, indirect, detection of gravitational waves came in the 1970s through observation of a pair of closely orbiting [[neutron stars]], [[PSR B1913+16]].<ref name="natgeo"/> The explanation for the decay in their orbital period was that they were emitting gravitational waves.<ref name="natgeo"/><ref name="Tf1T0"/> Einstein's prediction was confirmed on 11 February 2016, when researchers at [[LIGO]] published the [[first observation of gravitational waves]],<ref name="PRL-20160211"/> detected on Earth on 14 September 2015, nearly one hundred years after the prediction.<ref name="natgeo"/><ref name="CO6kH"/><ref name="oSmHb"/><ref name="hkKSp"/><ref name="38Msx"/>